You receive this quest from Mita in the River of the Addancs.
First, go get the Talk to the Addanc quest if you haven't already.
Then go to the River of the Addancs.
Go to the East teleport and face it looking East.
Do a 180 degree spin and take 2 steps West and touch the red bush.
Talk to Mita.
She asks you to finish building the bridge to the house in the middle of the river, and in exchange for helping, she'll give you the power to see Addancs.
You'll need the Iron Maul and five bags of wood.
Mita gives you the Iron Maul.
You will receive the Build the Bridge quest.
Ergon, who lives in Kentavon Canal, also sells bags of wood.
You can also get bags of wood from Inns on the island. Make sure you save before entering the Inns so if they don't have a bag of wood for sale, you can keep reloading that save until they do.
Return to the River of Addancs and equip the Iron Maul and walk over the bridge, which is on the East side of the river, and you will build it.
When you finish building the bridge, talk to George in the house and he will give you 5 Rune Gems for building the bridge.
Go back and talk to Mita.
The Build a Bridge quest will be solve.
You'll receive the Addanc Sight Ability and an increase in fame.
The Addanc Islada, who you need to talk to for Kill the Pirates quest will now be visible and is in Northern part of the River of Addancs.
Talk to her and you will commit a crime by stealing the Druidic Wand from her.